Andrew Moss, who resigned as Aviva chief executive after shareholders voted down the insurer's pay policies. Photograph: David Levenson/AFP/Getty Images

Anger over executive pay has escalated, claiming the scalp of the boss of Britain's biggest insurance company, Aviva, and inspiring a shareholder revolt at the bookmaker William Hill.

In what is seen as the latest manifestation of a "shareholder spring" – named after the Middle East uprisings last year – Andrew Moss, chief executive of Aviva, resigned with a £1.7m payoff. He finally quit after investors voted down the insurer's pay policies five days ago in protest at his pay and performance.

Ralph Topping, the chief executive of William Hill, was also under pressure after nearly half its shareholders – 49.9% – voted against its executive pay deals. The vote, which focused on the £1.2m retention package for Topping, was so close that some shareholders are considering asking for a recount. "It's a photo finish and should go to a steward's enquiry," said Sarah Wilson, chief executive of the shareholder advisory body Manifest.

The day of drama in the City came amid the biggest wave of shareholder activism since Labour first introduced the "say on pay" for shareholders a decade ago.

The business secretary, Vince Cable, intends to keep up the pressure on investors by meeting a group of the powerful institutional shareholders in the City. Hours later, the government will use the Queen's speech to set out its intention to hand investors more powers to clamp down on boardroom excess.

In recent weeks, David Brennan, chief executive of AstraZeneca, and Sly Bailey, chief executive of Trinity Mirror, have both stepped aside, while protests have been registered at a series of companies including Barclays, the mining firm Xstrata, and the Mr Kipling owner Premier Foods.

More protests are expected in the coming days as major companies – such as the British Gas owner Centrica, household products company Unilever and advertising group WPP – all hold annual meetings where investors must be allowed to vote on pay deals.

Cable, credited for encouraging the wave of shareholder activism through his consultation on executive pay, is likely to introduce a mandatory vote on future pay policies. It is not yet clear whether he thinks that the hurdle for a vote to pass should be raised from 50% to 75%.

The current vote, introduced a decade ago, is advisory and can be ignored by companies – as appears to be case at William Hill, where the chairman, Gareth Davis, brushed aside the protest vote.

As well as Cable's pressure on shareholders, the government's austerity measures are galvanising the attitudes of pension fund trustees in how they ask the big City managers to vote at annual meetings. "It's a perfect alignment of the planets," said Wilson. "Vince Cable's consultation on pay has focused shareholders' minds and there is increasing pressure from the end consumer about underperformance of companies."

L&G, which voted against 125 pay reports last year, is now getting pressure from its clients – big pension funds, for instance – about how it votes.

Sadan added: "It's a triangulation of austerity, of government – because the electorate are focusing on this – and we've had our clients asking us about it. Everyone in companies are getting zero or inflationary pay rises and it should be the same for executives who have to deal with morale in their companies as well."

But even before the annual general meeting season ends – it typically runs from April to June – there are concerns about keeping up the momentum and securing changes from companies. Some, such as Barclays and Aviva, made tweaks to pay deals before enduring pay protests. Barclays, for instance, put new conditions on a bonus for its chief executive, Bob Diamond, who took home £17m in 2011, while his counterpart at Aviva was forced to hand back a £46,000 pay rise that would have taken his salary above £1m.

Guy Jubb, the global head of governance and stewardship at Standard Life Investments, said: "If there is any dividend from this 'spring', it is the clear reminder to remuneration committees of the impact of not communicating effectively with shareholders."

Louise Rouse, director of engagement at FairPensions, which campaigns for voting at annual meetings, said: "Both political and public anger can pass. It is very important that this doesn't become a shareholders spring, that is that it isn't restricted to one season," Rouse said.